The present invention relates to semiconductor device fabrication and integrated circuits and, more specifically, to structures that integrate airgaps with a field-effect transistor and methods for forming a field-effect transistor with integrated airgaps.
Complementary metal-oxide semiconductor (CMOS) circuitry is utilized in mobile communication devices (e.g., laptops, cellular phones, tablets, etc.) to handle wireless high frequency signals transmitted to and/or received by the mobile communication devices. The circuitry may include a low noise amplifier and a high frequency switch that allows for high frequency signals received by an antenna to be routed from the low noise amplifier to other chip circuitry and for high frequency signals to be routed from a power amplifier to the antenna. The high frequency switch may include a stack or bank of field-effect transistors formed by CMOS processes. Field-effect transistors fabricated on a bulk substrate may exhibit poor linearity due to, for example, non-linear electric fields on the substrate and poor intermodulation properties. Semiconductor-on-insulator (SOI) substrates may mitigate some of these issues, but are costly in comparison with bulk substrates.
Improved structures that integrate airgaps with a field-effect transistor and methods for forming a field-effect transistor with integrated airgaps are needed.